1. Field of the Invention
The invention relates to an optical rotary joint, and also to a micro-optical system such as a collimator for optical beam guiding or beam shaping.
2. Description of the Related Art
Various transmission systems are known for transmitting optical signals between units that are rotatable relative to each other.
An optical rotary joint for a plurality of channels, having a Dove prism as a derotating element is disclosed in U.S. Patent Application Publication No. 2005/0036735. Light from supply light-waveguides is coupled via collimators into a Dove prism, derotated by means of the latter, and fed into leading-away light-waveguides via further collimators. In order to render the arrangement independent from the refractive index of a medium in the surroundings of the Dove prism, the prism is provided with supplementary optical members which ensure perpendicular light entry. Owing to this perpendicular light entry, no refraction occurs at the transition face. A disadvantage of this is the partial reflection of light at the perpendicular transition face, so that at least a portion of the light is coupled back into the light-waveguide. This results in a relatively small return loss.
Another kind of optical rotary joint is disclosed in International Publication No. WO 01/98801. This describes a micro-optical system having optical and mechanical components as a one-piece constituent part. With this design a substantially higher packing density of the individual glass fibers can be attained. Once again, the parallel light-entry and light exit faces are of disadvantage, as they cause a relatively small return loss.
It is a disadvantage of the known prior art that relatively strong reflections of the transmitted light arise inside the rotary joint or at the collimators. An improvement can be achieved with vapor-coated intermediate layers, the refractive indices of which lie between the refractive index of the optical components and that of the surroundings. However, with different surrounding media such as air or oil it is also necessary to adapt the intermediate layers.